Altitudinal trends in species richness and diversity of Mesoamerican parasitoid wasps (Hymenoptera: Ichneumonidae)

1. Utilising short-term but geographically extensive sampling in Guatemala, Honduras, and Nicaragua, we examined altitudinal trends in species richness and diversity of ichneumonid parasitoid wasps. This study covered 19 subfamilies, including four globally large subfamilies that have not yet been taxonomically revised in the Neotropics. 2. Sampling was done at 25 sites classified into three elevational categories on the basis of the average elevation of traps at each site (low 34-659 m a.s.l., middle 1033-1709 m a.s.l., and high 1930-2565 m a.s.l.). A total of 2847 ichneumonid individuals were captured and sorted into 751 morphospecies, most of which were identified to the genus level. 3. We found a clear compositional gradient in ichneumonid communities along the elevational gradient, as the majority of species were restricted to either one elevational zone or two adjacent zones. In our data, mid- and high-elevation sites had generally higher ichneumonid species richness and diversity than low-elevation sites. These trends were largely similar to those found in larger scale Mesoamerican ichneumonid studies. 4. Yet, the low ichneumonid richness at low elevations may partly be a sampling artefact. This provides a new piece of evidence for the suggestion that extensive sampling is needed for uncovering the real diversity of ichneumonids in tropical lowland forests, and that the reputation of Ichneumonidae as a notable example of a reversed latitudinal diversity gradient may be undeserved.